I think Oda had adv CoC in mind since Katakuri vs Luffy.
Remember, unlike the usually CoC clashes(Doflamingo vs Luffy or Don vs Luffy), Katakuri had Luffy used CoC without touching:
The only characters who show something like that are Yonkou, Roger vs Whitebeard...
I think Katakuri indeed has adv CoC, but just at lowest lvl, a reason why he only could coat few of his attacks in CoC.
As example when he was in rage or when he used awakening power mochi for the first time.
The reason why Zangari mochi had so much lightning was because Katakuri probably used all his CoC in that move.
The next time we see Katakuri(as
@Kurozumi Wiwi said) gonna have adv CoC too.
Now I agree with the thread thought, it is very hard to see which character has adv CoC or not.
I think these which have a shockwave also in the attack(Garp,Kuzan,Big Mom) are clearly adv CoC users.